This invention pertains to portable devices for providing heated air to any particular desired point. In many instances such devices may use a heat producer such as that of applicant's U.S. Pat. No. 5,819,724, issued Oct. 13, 1998, but they may also be used where the heat is produced by some other type of heater. Usually the transmission of heat is a heated oil or similar fluid. Ordinarily the heater is driven by an engine and is enclosed in a housing having an inlet and a directed outlet.
Particularly in very cold climates where the ambient air is drawn into the heat exchanges, there may be times when the air is not adequately heated for use in heating the desired area or where the heated air needs to be better controlled.
In order to do that added heating or to get improved control, this invention proposes a fairly simple recirculating device. Controls are necessary and provide for the appropriate outlet temperatures and amounts of flow.